Cellular Control 6.1.1 Flashcards
What is a gene mutation
A change in the base sequence of DNA molecule that may result in an altered polypeptide
When do these gene mutations occur?
During S phase of DNA replication
Gene mutations are more likely to occur when:
If You are exposed to mutagenic agents which can interfere with DNA replication
Give a few examples of mutagenic agents.
-high energy radiation (UV light)
-ionising radiation (Gamma rays + X-rays )
-chemicals (carcinogens e.g. mustard gas, cigarette smoke)
What can a gene mutation lead to?
Could result in either:
-a base being deleted or substituted for a different one
This is the regional DNA sequence=
TAC CCA AGT GGC
What type of mutation is this? 1
TAC ACA AGT GGC
What type of mutation is this? 2
TAC CAA GTG GC
- Base substitution mutation
- Base deletion mutation (frameshift)
What is a base substitution mutation ?
-gene mutation
-one nucleotide is incorrectly swapped during DNA replication for another nucleotide
-the correct nucleotide is replaced with an alternative nucleotide
-effects are small
Why might base substitution be considered silent?
Meaning that the new codon still codes for the same amino acid- this is because genetic code is degenerate ( multiple codons can code for the same amino acid) so no change in the sequence and so polypeptide chain likely wont be affected
What is a base deletion mutation?
-gene mutation
-a nucleotide is skipped/absent from the replicated strand
-causes frameshift mutation
-effects can be damaging
Frameshift mutation= removal of one base changes all of the subsequent codons
-more harmful as multiple amino acids may be incorrectly coded for
What is insertion mutation?
-gene mutation
-an extra nucleotide (with a new base) is randomly incorporated into the DNA sequence during replication
Define gene
Section of DNA, coding for a polypeptide
What is a chromosomal mutation?
A change in the structure or or number of chromosomes which can alter the genetic code
What is a mutation?
- a random change in the quantity or structure of the DNA of an organism
-it can happen in the body (somatic) or reproductive cells (germ-line)
What is a point mutation/substitution?
Occurs when one base pair is replaced by another
Mutations occur:
Spontaneously and continuously
Why do mutations usually not have an effect on us?
-as most mutations do not alter the polypeptide or only alter it slightly so that its structure or function is not changed (as the genetic code is degenerate I.e. several different triplets often code for the same amino acid)
-Many mutations occur in non-coding sections of DNA and so have no effect on the amino acid sequence at all
An insertion mutation changes the _________ that would have been coded for by the ___________ ____ _______, as it creates a ___, different triplet of _____.
An insertion mutation changes the amino acid that would have been coded for by the original base triplet as it creates a new different triplet of bases
How does a mutation lead to a change in the polypeptide?
-DNA base sequence determines the sequence of amino acids that make up a protein
-mutation in a gene can lead to a change in the base sequence
-and consequently the amino acids that are coded for
- If these amino acids change then the polypeptide and so protein will change in terms of structure or function
Substitution mutations can take 3 forms:
- Silent mutation
- Missense mutation
- Nonsense mutations
What is a silent mutation?
-no change to the primary structure of the polypeptide despite a change in the nucleotide base as it does not alter the amino acid sequence
In a silent mutation why does a change in the base sequence not lead to a change in the polypeptide?
Because DNA is degenerate and certain codons may code for the same amino acid, leading to no change in the amino acid sequence and therefore no change to the primary structure of the polypeptide
What is a missense substitution mutation?
The mutation alters a single amino acid in the polypeptide chain
Give an example of a disease caused by a single substitution mutation changing a single amino acid in the sequence
Sickle cell anaemia
What is a nonsense mutation?
-mutation creates a premature stop codon
What is a stop codon and its function?
Signal for the cell to stop translation of the mRNA molecule into an amino acid sequence
How does the stop codon affect the polypeptide chain or protein?
Signal for the cell to stop translation of mRNA molecule into an amino acid sequence, causing the polypeptide chain produced to be incomplete and therefore affecting the final protein structure and function
Produce shorter polypeptide chain—> likely to fold differently (depending on how early in the sequence)—-> functionality of protein likely to change
Give an example of a disease caused by a non-sense mutation
Cystic fibrosis- although it not always just only caused by a non-sense mutation
What is a frameshift mutation?
-complete change to the entire amino acid sequence of a protein after the mutation site
-because of the way the translated mRNA is read by the ribosomes
-mRNA is read in codons, groups of 3 nucleotides
-if an additional 1 or 2 nucleotides are added or removed the sequence is ‘shifted’
-translation machinery cannot know that there has been an error, and still reads the sequence in triplet codons
-the entire mRNA and resulting protein are therefore completely different in terms of structure and/or function
In terms of the effects of mutation, what different effects of gene mutations can you have?
-Beneficial mutations
-Harmful mutations
-Neutral mutations
What do we mean by a beneficial mutation?
-alteration to a polypeptide may result in an altered characteristic or function in an organism that causes beneficial effects e.g. enhanced function of a protein
Give an example of each of the following:
-beneficial mutation
-harmful mutation
-neutral/causes of mutations
-Beneficial= rare but often leads to evolution, an example is production of the pigment melanin
-Harmful= cancer, genetic diseases haemophilia, sickle cell anaemia, cystic fibrosis
-Neutral mutation= no effect, e.g.the ability to taste a bitter-tasting chemical found in Brussels sprouts
What is a harmful mutation??
-alteration in the polypeptide may result in an altered characteristic in an organism that causes harmful mutation e.g. malfunctioning of a protein made
Explain how Cystic fibrosis is an example of a deletion mutation?
-in aroun 70%= the mutation that causes disease is deletion mutation
-of 3 nucleotides in the gene coding for the protein CFTR
-the loss of function of CFTR protein caused by this deletion mutation results in symptoms e.g. lung and pancreatic problems as a result of extremely thickened mucus
Explain how a mutation can be neutral and have no effect?
-mutation might not alter the polypeptide
-mutation may alter polypeptide slightly so its structure and function is not changed
-mutation alters structure/function of polypeptide but resulting difference in characteristic provides no particular adv/disadv to the organism
What are insertion and deletions?
Frameshift mutation
Insertion and deletion causes frameshift mutation. What is frameshift mutation?
-disrupts triplet code reading
-every codon after mutation affected
-protein will have diff sequence of amino acids
-so a diff tertiary structure
-t/f protein no longer performs correct/ same function
Significance of genetic code being degenerate on mutations
-Multiple codons code for particular amino acid
-point mutation may have no effect
-make same protein for normal functioning
How does a missense substitution mutation affect the protein?
Change to primary structure ——-> change to tertiary structure & overall 3D shape of protein——-> functionality of protein likely to change
What happens to reading frame when frameshift mutation occurs?
Reading frame now lines up different triplets after point of mutation, genetic code is non-overlapping & each base is only read once
What are chromosomal mutations?
Large sections of chromosomes altered
What is a chromosomal deletion mutation??
Sections of chromosome deleted
What is a chromosomal duplication mutation?
Sections of chromosome (or entire chromosome) duplicated
What is a chromosomal translocation mutation?
Section of chromosome joins another non-homologous chromosome
What is a chromosomal inversion mutation?
Section of chromosome turned upside down
What are the different levels of control?
- Transcriptional- turning genes o/off- DNA more tightly wound around histone proteins during cell division
- Post-Transcriptional- editing RNA
- Translational- turning translation on/off
- Post-translational- editing protein
Evaluate whether a base deletion mutation has a bigger effect on polypeptide structure than a base substitution mutation?
-sub can result in a silent mutation+ no change to primary structure
-sub only changes a single amino acid
-sub does not change the no. Of amino acids whereas deletion reduces by 3
-deletions are frameshift mutation, every amino acid downstream of mutation changes
-however sub can change codon to a stop and if this occurs near the start of the sequence, impact is significant
Why can substitution mutations can be silent?
Because genetic code is degenerate
What is gene regulation?
The control of gene expression
The nucleus of every cell in the human body contains the _____ genes. However not every gene is_________ in every cell. In addition not all genes are expressed ____ the times.
a) same
b)expressed
c)all
What are regulatory mechanisms?
Several mechanisms which exist within cells to make sure the correct genes are expressed in the correct cell at the correct times
What are the types of regulatory mechanisms/levels of control?
Transcriptional
Post transcriptional
Translational
Post translational
What is a structural gene?
Codes for any RNA or protein that has a function within cell e.g. enzymes, membrane carriers, hormones etc.)
-makes any protein product other than a regulatory factor
What is a regulatory gene?
code for proteins (or various forms of RNA) that control the expression of structural genes
-the product of these genes control the expression of structural genes
If the ________ genes being controlled are in any way are involved in the process of transcription, then gene ________ is occurring at the ___________ level.
If the structural genes being controlled are in any way are involved in the process of transcription, then gene control is occurring at the transcriptional level.
Movement of transcription factors
-transcription of a gene will only occur when a molecule from the cytoplasm enters the nucleus and binds to the DNA in the nucleus
What is a transcription factor?
protein molecules which can each bind to different complimentary base sequences on DNA and therefore initiate or inhibit transcription of genes- to control protein synthesis
What happens when a transcription factor is bound to a complimentary base sequence on DNA
Once bound transcription begins, creating the mRNA molecule for that gene which can then be translated in the cytoplasm to create the protein
Without the binding of a transcription factor the…
the gene is inactive and the protein wont be made
How can the rate of transcription be changed?
Transcription factors can either initiate or inhibit transcription and therefore controlling protein synthesis—–> can turn on/off genes so only certain proteins are produced in a particular cell
What enables genes to become specialized in a cell?
-turning on/off particular genes in a cell is what enables them to become specialized
What is the transcriptional level of gene expression?
-transcription regulatory factors bind to DNA near structural genes to switch genes on (activator) or off (repressor) by:
-altering conditions to allow RNA polymerase to bind
(e.g. a transcription factor binding to the promoter region of a gene which allows RNA polymerase to bind and for transcription to occur )
—>prokaryotes= lac operon
—>eukaryotes=modification of histone proteins for chromatin remodeling
-regulation of gene expression during mRNA production- by altering the rate of transcription of genes
Faster rate of transcription= more protein made
Slower rate of transcription= less protein made
-
What is heterochromatin?
tightly wound DNA in cell division e.g. in Prophase, can be seen as chromosomes
How do we get transcription to occur from heterochromatin?
We form a euchromatin by acetylation or phosphorylation
-addition of acetyl groups decreases positivity of histones
-they are less attracted to phosphate on DNA
-DNA and histones weakly associate
-histone acetylation results in loose packing of nucleosomes
-transcription factors can bind to the DNA and genes are expressed
Describe the process of acetylation?
-addition of acetyl groups decreases positivity of histones
-they are less attracted to phosphate on DNA
-DNA and histones weakly associate
-histone acetylation results in loose packing of nucleosomes
-transcription factors can bind to the DNA and genes are expressed
What is euchromatin?
loosely wound DNA in cell division e.g. in interphase, can’t be seen as chromosomes
What is a chromatin?
Is the DNA in our cells along with the proteins associated with it called Histones
Why can transcription only occur in euchromatin?
because there’s space for RNA polymerase to attach to the promoter region
How to form heterochromatin from euchromatin?
methylation—-> increases hydrophobic nature of histones
Define epigenetics
-a heritable change in gene function without changing the DNA base sequence
-caused by the environment
-can inhibit transcription
What two types of epigenetics prevent transcription?
-increased methylation
-decreased acetylation of histones
How does increased methylation inhibit transcription?
-methyl groups that are added to DNA attach to cytosine bases
-this prevents transcription factors from binding
-and attracts proteins that condense the DNA histone complex
-in this way methylation prevents a section of DNA from being transcribed
W
How does decreased acetylation inhibit transcription?
-removal of acetyl groups increased positivity of histones
-they are attracted to phosphate of DNA
-DNA and histones strongly associate
-makes it hard for transcription factors to bind
Euchromatin- ‘active’= how do we increase transcription?
-decrease methylation
-increased acetylation of associated histone proteins
Heterochromatin ‘silent’= how do we decrease transcription?
-increased methylation
-of DNA inhibits transcription
-decreased acylation of associated histone proteins on DNA inhibits transcription
What is an operon?
-usually found in prokaryotic cells (more common in pro than eu)
-groups of simultaneously controlled genes that are either all expressed or not
What is a lac operon?
-operon present in e.coli
-is a sequence of 3 gene= lac Z, lac Y, lac A
-collectively aid digestion of lactose
When is lac operon used?
When glucose is unavailable
RNA polymerase only binds to promoter…
with the presence of a transcription factor
How are transcription factors activated in eukaryotes?
-hormone enters cell and binds to inactive transcription factor and activates it
-active transcription factor binds to promoter and enables RNA polymerase to bind to promoter
-RNA polymerase transcribes structural genes
How can estrogen stimulate the transcription of a gene?
-estrogen=lipid soluble molecule so can easily diffuse through plasma membrane of cells
-binds to inactive transcription factor (estrogen receptor(contained within protein complex)) and activates it
- estrogen/hormone does this by causing a change in the shape of the receptor
-as a result receptor moves away from protein complex its normally attached to and binds to promoter region of one of its target genes
-estrogen receptor attracts other cofactors to bind with it
-this allows RNA polymerase to bind to promoter
-RNA polymerase transcribes structural genes
How are transcription factors activated in eukaryotes?
- Hormone enters cell and binds to inactive transcription factor and activates it
- Active transcription factor binds to promoter and enables RNA polymerase to bind to promoter
- RNA polymerase transcribes structural genes
State and describe 2 transcription factors.
Activators= speed up transcription
Repressors= slow down transcription
Transcription regulatory factors bind to DNA near structural genes to switch genes on (activator) or off (repressor)
How do transcription factors affect hormones/sugars?
-they bind to the transcription factor
- increase or decrease binding to the DNA
-so the molecules present in the cells environment can control protein synthesis by transcription factor binding
Summaries the process by which transcription factors initiate transcription
-DNA binding site binds to complimentary base sequence
-allows RNA polymerase to bind
-transcription begins and creates the RNA molecule for the genes which can then be translated
Transcription control in prokaryotes vs eukaryotes
Prokaryotes:
-RNA polymerase can bind to promoter without transcription factor
-transcription factors bind to operators
-transcription factor inhibits gene expression
-transcription factor named repressor protein
Eukaryotes:
-RNA polymerase can only bind to promoter with transcription factor
-transcription factors bind to promoters
-transcription factors stimulate gene expression
-transcription factor named transcription factor
Process of lac operon when glucose is present?
1.LacL expressed to make repressor protein, which binds to operator, blocking promoter (RNA polymerase binding site)
- RNA polymerase cannot bind to promoter due to blockage —> no transcription of structural genes
- CRP binds to cAMP—>up-regulates activity of RNA polymerase
- glucose decreases cAMP conc. inside cell—> CRP- cAMP- RNA polymerase complex dissociates—-> down regulating transcription
What 3 genes does the lac operon contain?
LacZ, LacY, LacA
What is LacL?
regulatory gene found near operon which codes for a repressor protein- that inhibits transcription when there is no lactose present
What is a repressor protein?
A protein that inhibits transcription
How does LacL control transcription?
-when lactose is absent, repressor protein is constantly produced
-repressor protein binds to operator (a region close to the operon) to prevent RNA polymerase from binding to DNA at the promoter region
-this inhibits transcription
-when lactose is present, it binds to the lac repressor protein
-causes changes in tertiary shape so can no longer bind to operator
-allows RNA polymerase to bind to promoter
-so structural genes can be transcribed
-initiating transcription
Why is the lac operon only needed when glucose isn’t present?
-because bacteria require less energy to digest glucose than lactose, so glucose is the favorable respiratory substrate
- if glucose isn’t present, then lactose is digested
-lac operon proteins only needed when/if glucose is absent and lactose is present
-this regulates transcription of these genes to meet demands
Operons are more common in prokaryotes than eukaryotes, suggest why?
-prokaryotes= smaller organisms=have smaller genomes= made up of one cell that only needs to respond to change in its environment
-eukaryotes= multicellular organisms= made up of many cells forming tissues and organs, coordination between many cells requires more complex transcription control than operons can provide
Describe what happens when lactose is not present
regulatory gene (LacL) produces lac repressor (transcription factor that binds to operator)
—-> blocks transcription as RNA polymerase cant bind to promoter
Structural genes of lac operon
lacZ, lacY, lacA
Why does e.coli use the lac operon?
- E.coli respires lactose if glucose is unavailable
- lac operon=genes that produce enzymes needed to respire lactose
- structural genes on lac operon priduc proteins to digest lactose (β-galactosidase and lactose permease)
What is the role of cyclic AMP?
-increases the rate of transcription of lac operon
-because when transcription is initiated by repressor removal, it is still too slow to create required amount of enzymes
What is the role of cAMP receptor protein? (CRP)
-binds to lac operon to produce lacZ, lacY and lacA
-CRP only binds once bound to cAMP
-when bound to cAMP first it then binds to lac operon to produce lacZ, lacY, lacA and so increase the rate of transcription
Which is bigger DNA or gene?
DNA is the larger structure that contains genes
What is a gene?
segment of DNA that contains a sequence of instructions for making specific proteins or molecules e.g. hormones
What are introns?
non-coding regions within genes- these sequences are not translated (they do not code for any amino acids)
What are exons?
coding regions within a gene- these are sequences which will eventually be translated into amino acids that will form the final polypeptide
All DNA of a gene including introns and exons are transcribed to form a strand called _______ ____.
All DNA of a gene including introns and exons are transcribed to form a strand called primary mRNA.
Primary mRNA is edited during a process called________, where ________ are removed leaving only ____ _____ which are complimentary to original ____ ________
called splicing
introns are removed
leaving only RNA exons
complimentary to original DNA exons
What is pre-mRNA? (primary mRNA transcripts)
introns/exons copied into mRNA
Control of gene expression- post transcriptional (modifying mRNA)
- RNA splicing—>remove introns
- Addition of protective caps (5’cap)
3.Add a poly adenine tail at the 3’ end —-> stabilize mRNA (prevents degradation)—-> mature mRNA
-editing of primary mRNA: alternative splicing:
-mRNA sliced in different ways , allowing single gene to result in creation of multiple proteins
( -diff versions of mRNA, make diff proteins of diff functions )
when transcription of a gene occurs both introns and exons are transcribed.
But this is not what happens due to a process known as splicing. Explain what is splicing and why it occurs.
-means mRNA also contains introns and exons (this RNA molecule is often referred to as pre-mRNA or primary mRNA)
-as introns are not to be translated they must be removed from pre mRNA molecule
-exons then all fuse together to form continuous mRNA molecule called mature mRNA that is ready to be translated
-process is known as splicing and ensures only coding sections of mRNA are used to form proteins by translation (if any introns were included in mature mRNA, resulting protein would not be formed properly and may dysfunction
Regulatory mechanism that controls gene expression at post-translational level
Modifying polypeptides to make proteins of specific functions:
- Addition of non-protein groups e.g. lipoprotein, glycoprotein
- folding/shortening/modifying proteins, so that they are folded into a unique 3D tertiary or a quaternary structure and bonds form to hold them in this shape/structure
- Modification of cAMP (activation):
-cAMP+ CRP—-> bind to RNA polymerase= when cAMP levels are high it binds to CRP, causing change in CRPs shape, this altered CRP then recruits/aids RNA polymerase to binds to specific DNA sequences, enhancing expression of certain genes, by increasing rate of transcription
-cAMP activates protein kinases e.g. kinase A (also known as PKA) —-> activate other enzymes/proteins
Where does splicing occur?
Nucleus
why is cAMP needed?
some proteins require activation before they can work by hormones or sugars
Functions of cAMP?
- activates proteins by altering their 3D structure
- activates protein kinases which activate proteins by catalyzing addition of phosphate (phosphorylation)
- Changes inactive precursors of enzymes (by hydrolysis revealing the active site or changing the configuration to reveal the active site) to become an active enzyme
What is alternative splicing?
concept that splicing occurs in many ways and allows a single gene to result in many proteins being created
using 3 words describe splicing
removal of introns
What is a promoter?
-signal to start transcription
-sequence of DNA
-where RNA polymerase binds
What is an operator?
set of structural genes
Define gene expression
conversion of the information encoded in a gene into a functional gene product
-usually a protein but sometimes just RNA
Describe the post transcriptional level of regulation
regulation of gene expression after mRNA production
Why will a gene not bound to a transcription factor be inactive?
RNA polymerase cannot bind so transcription is inhibited
What makes a suitable respiratory substrate?
-bonds that contain energy so can be broken
-soluble so can move
-H/OH groups that can bond with water molecules
What is a homeobox sequence?
-group of regulatory genes 180 bp—–> codes for homeodomain
-control body development
-highly conserved—-> regulated mitosis & apoptosis—–>respond to internal and external stimuli
Homeobox genes
sequence of genes which create proteins, that regulate the expression of other genes involved in the early development of body formation in the embryo
genetic control is important because…
it determines development of features
a) Homeobox genes code for
b) in order to
a) transcription factors
b) regulate gene expression important in development
What are hox genes?
groups of homeobox genes found in animals——> responsible for position of body parts
Homeobox genes are highly conserved what does this mean?
they have not involved much
Role of hox genes.
-responsible for correct body development and body part positions
-order of these genes in the DNA is the order in which their effects are expressed on the organism
Many animal bodies are S_________ and have S________
Many animal bodies are segmented and have symmetry
Give an example of how animal bodies can be segmented
E.g.
-the segments on an insect
-rings on a worm
-vertebrae in the backbones of vertebrates
Give examples of how animal bodies have symmetry
-jellyfish have radial symmetry, so a head end and a non head end/tail end
-some organisms e.g. humans have bilateral symmetry, humans, meaning they have a left and right side
What factors affect homeobox development
Internal stimuli:
-hormones
-psychological stress
External stimuli:
-temp
- drugs e.g. thalidomide
What are homeodomain?
Part of protein that is coded by homeobox sequences
What is a homeobox?
-code for homeodomain
-bind to DNA to switch genes on and off——> control body plan
How does the sequence/order of box genes determine the development?
Head tail oriented, segments, position of limbs, and position of eyes
State 3 reasons why fruit flies are chosen/ are ideal to use for genetic research e.g. homeobox genes
-simple genetics/body plan
-short life cycle- rapidly reproduce
-cheap and easy to obtain+ keep a large sample
Suggest 3 reasons why mice are chosen as a suitable species for investigating homeobox genes?
-share more genes with humans/ a lot of genes with humans
-show effects are generalisable to more than one species
-cheap
For lactose to enter cytoplasm, a protein is required. Why are young mammals more likely to contain this protein in E.coli than old mammals?
-diet is high in milk - t/f high lactose concentration
-gene for the protein channel is switched on
Explain why some regions of DNA are described as non-coding
-introns are removed
-not present in mature mRNA and so cannot be translated
-regulatory genes
Suggest why non-coding regions of DNA show more variation?
-doesn’t affect survival
What is the importance of mitosis in genetic control?
It increases number of cells, resulting in growth
What is apoptosis?
Programmed cell death and removes unwanted cells
Why do we need apoptosis?
To brea down cells e.g. between fingers and toes
What causes lack of apoptosis?
Hox gene hasn’t produced transcription factors t/f molecules signalling apoptosis haven’t been made so apoptosis doesn’t occur
The cell cycle is controlled by _____, so new cells are only made when needed for _______ ____ ________ which _______ ______ _____ ___ _____ ______.
The cell is controlled by genes.
So new cells are only made when needed for growth and repair.
Which prevents tumour growth and conserves energy
When does apoptosis occur?
-if the cell is too old to function
-if an error in the cell cycle is detected
-then cell is destroyed and resources are recycled
Mitosis and apoptosis is regulated by………which are impacted by ———-. The effect of this is highest during……
Mitosis and apoptosis is regulated by hox genes
which are impacted by external stimuli e.g. temperature and internal stimuli e.g. hormones, psychological stress etc.
The effect of this is highest during growth and development.
How does apoptosis work?
-Breaks up content e.g. nucleus
-cell membrane shrinks into projections called blebs
What do blebs turn into?
Apoptotic body
Contains an organelle of types of organelles
Apoptotic bodies are engulfed by
Phagocytes in phagocytosis
State 3 roles of mitosis other than growth and repair
-asexual reproduction
-development of body plan
-increasing no. Of stem cells
Explain how failure of the control mechanism in hox genes can lead to deformities
Hox genes:
-hasn’t produced transcription factors
-t/f molecules signalling apoptosis haven’t been made
-so apoptosis doesn’t occur
Explain the process of apoptosis
- Triggered by transcription factors made by hox genes causing cytoskeleton to be broken down by enzymes
- ‘Blebs’ form due to changes in the cell surface membrane
- Blebs form segments which are digested by phagocytosis
What changes would make a gene more likely to be transcribed?
Increasing acetylation of histone proteins
True or false:
Epigenetic changes can sometimes be removed
True
True or False:
If damaged DNA is detected at the G2 checkpoint, the cell cycle is halted and the cell tries to repair damage
True
RNA nucleotides are activated by addition of phosphate groups from …?
ATP
Define Regulatory gene
-make repressor proteins
-product switches gene on or off
What are transcription factors?
Proteins that bind to DNA and switch genes on or off
What is an activator?
Transcription factor that increases the rate of transcription
What is a repressor?
Transcription factor that decreases the rate of transcription
Where do transcription factors bind in eukaryotes?
Specific DNA sites near start of their target genes
Where do transcription factors bind in prokaryotes?
Onerous
What is an operon
Cluster of genes under control of a promoter
What is an operator?
DNA sequence where repressor binds to
What is a promoter
DNA sequence where RNA polymerase binds to
What do structural genes code for?
Proteins not involved in DNA regulation——> enzymes:
- β-galactosidase
- Lactose permease
- Lactose transacetylase
What do the control elements include?
Promoter and operator
What do regulatory genes (lacL) code for??
Activator or repressor
What is a body plan?
General structure of organism
what do transcription factors in eukaryotes not contain that prokaryotes do ?
operator
difference between structural genes & regulatory genes
Structural genes code for proteins that have a function in cell, regulatory genes produce transcription factors or repressor proteins. Regulatory genes control
expression of structural genes.
Lactose-intolerant adults, who do not produce lactase into adulthood, experience digestive issues if they consume milk.
However, lactose-intolerant adults do not experience digestive issues if they consume yoghurt.
Yoghurt is produced from milk that has been fermented by bacteria carrying out anaerobic respiration.
Suggest why lactose-intolerant adults can safely consume yoghurt.
no lactose present in yoghurt as been digested by bacteria during anaerobic respiration into other sugars.
severity of mutations of hox genes ?
Often lethal
In order for lactose to enter the cytoplasm of E. coli a protein is required.
The E. coli living in the digestive system of young mammals are more likely to contain this protein than
E. coli living in the digestive system of old mammals.
Suggest an explanation for this observation.
-young mammals’ diet: high in milk ~> high lactose concentration
- lactose permease gene switched on
Suggest how allele B inhibits the expression of allele A.
- B codes for repressor protein
- protein binds
to, promoter - product of allele B stops, transcription
- product of B inhibits enzyme
Explain how failure of the control mechanism during development could lead to a deformity where individual has webbed fingers ?
- hox gene does not produce transcription
factor - molecules signalling apoptosis not
produced - apoptosis does not
occur
These are examples of mutations:
Describe the effect of the mutation and explain how it might affect the protein produced
THE FAT OLD CAT SAW THE DOG (original)
THE EFA TOL DCA TSA WTH EDO G
THE ATO LDC ATS AWT HED OG
THE FAT OLD BAT SAW THE DOG
THE FAT OLD CAT SAW THE DOG
=origional
THE EFA TOL DCA TSA WTH EDO G
=insertion mutation
THE ATO LDC ATS AWT HED OG
= deletion mutation
THE FAT OLD BAT SAW THE DOG
= substitution (point)
